Merge branch 'cu-iosperf' into catch-up-2026-11

App.tsx

@@ -45,20 +45,14 @@ import { addUnifiedPushEndpointListener } from './src/lib/unified-push';
 // Pause between a mute change and the push-filter update it sends (#78).
 const MUTES_RESYNC_DELAY_MS = 1_000;
 import type { MainTabsParamList, RootStackParamList } from './src/navigation/types';
-import ComposeScreen from './src/screens/ComposeScreen';
 import EmailThreadScreen from './src/screens/EmailThreadScreen';
-import EmailSourceScreen from './src/screens/EmailSourceScreen';
 import LoginScreen from './src/screens/LoginScreen';
 import MailTab from './src/screens/MailTab';
-import FilesScreen from './src/screens/FilesScreen';
-import CalendarScreen from './src/screens/CalendarScreen';
-import ContactsTab from './src/screens/ContactsTab';
 import ContactDetailScreen from './src/screens/ContactDetailScreen';
-import ContactFormScreen from './src/screens/ContactFormScreen';
 import GroupDetailScreen from './src/screens/GroupDetailScreen';
 import SettingsScreen from './src/screens/SettingsScreen';
-import ScheduledScreen from './src/screens/ScheduledScreen';
-import UnifiedInboxScreen from './src/screens/UnifiedInboxScreen';
+// Screens that aren't on the way to the inbox load on first visit
+// (getComponent below), so their modules stay out of the startup work.
 import { useAccountStore } from './src/stores/account-store';
 import { useAuthStore } from './src/stores/auth-store';
 import { useCalendarStore } from './src/stores/calendar-store';
@@ -322,7 +316,7 @@ function MainTabsNavigator({ navigation }: NativeStackScreenProps<RootStackParam
       </Tab.Screen>
       <Tab.Screen
         name="Calendar"
-        component={CalendarScreen}
+        getComponent={() => require('./src/screens/CalendarScreen').default}
         options={{
           title: tabLabels.calendar,
           tabBarButtonTestID: 'tab-calendar',
@@ -338,7 +332,7 @@ function MainTabsNavigator({ navigation }: NativeStackScreenProps<RootStackParam
       />
       <Tab.Screen
         name="Contacts"
-        component={ContactsTab}
+        getComponent={() => require('./src/screens/ContactsTab').default}
         options={{
           title: tabLabels.contacts,
           tabBarButtonTestID: 'tab-contacts',
@@ -354,7 +348,7 @@ function MainTabsNavigator({ navigation }: NativeStackScreenProps<RootStackParam
       />
       <Tab.Screen
         name="Files"
-        component={FilesScreen}
+        getComponent={() => require('./src/screens/FilesScreen').default}
         options={{
           title: tabLabels.files,
           tabBarButtonTestID: 'tab-files',
@@ -904,10 +898,10 @@ export default function App() {
       <Stack.Navigator screenOptions={{ headerShown: false, freezeOnBlur: true }} screenLayout={withHosts}>
         <Stack.Screen name="MainTabs" component={MainTabsNavigator} />
         <Stack.Screen name="EmailThread" component={EmailThreadScreen} />
-        <Stack.Screen name="EmailSource" component={EmailSourceScreen} />
+        <Stack.Screen name="EmailSource" getComponent={() => require('./src/screens/EmailSourceScreen').default} />
         <Stack.Screen
           name="Compose"
-          component={ComposeScreen}
+          getComponent={() => require('./src/screens/ComposeScreen').default}
           // A tablet shows the composer as a panel over the screen it came
           // from, so that screen stays drawn behind the dimmed backdrop.
           options={isSplit
@@ -917,15 +911,15 @@ export default function App() {
         <Stack.Screen name="ContactDetail" component={ContactDetailScreen} />
         <Stack.Screen
           name="ContactForm"
-          component={ContactFormScreen}
+          getComponent={() => require('./src/screens/ContactFormScreen').default}
           options={{
             presentation: 'modal',
             animation: 'slide_from_bottom',
           }}
         />
         <Stack.Screen name="GroupDetail" component={GroupDetailScreen} />
-        <Stack.Screen name="Scheduled" component={ScheduledScreen} />
-        <Stack.Screen name="UnifiedInbox" component={UnifiedInboxScreen} />
+        <Stack.Screen name="Scheduled" getComponent={() => require('./src/screens/ScheduledScreen').default} />
+        <Stack.Screen name="UnifiedInbox" getComponent={() => require('./src/screens/UnifiedInboxScreen').default} />
         <Stack.Screen
           name="AddAccount"
           options={{

metro.config.js

@@ -33,4 +33,14 @@ if (process.env.BULWARK_MODULE_TIMINGS) {
   }
 }
 
+// Evaluate a module when it is first used instead of all of them before the
+// first render. Expo's default leaves this off; React Native's own template
+// turns it on. Side-effect-only imports (`import './x'`) still run in place.
+config.transformer.getTransformOptions = async () => ({
+  transform: {
+    experimentalImportSupport: true,
+    inlineRequires: true,
+  },
+});
+
 module.exports = config;

src/api/__tests__/jmap-client-session-cache.test.ts

@@ -0,0 +1,294 @@
+import { describe, it, expect, vi, beforeEach, afterEach } from 'vitest';
+
+const secure = new Map<string, string>();
+vi.mock('expo-secure-store', () => ({
+  setItemAsync: vi.fn(async (k: string, v: string) => { secure.set(k, v); }),
+  getItemAsync: vi.fn(async (k: string) => secure.get(k) ?? null),
+  deleteItemAsync: vi.fn(async (k: string) => { secure.delete(k); }),
+}));
+
+import AsyncStorage from '@react-native-async-storage/async-storage';
+import { JMAPClient, AuthenticationError, SessionSupersededError } from '../jmap-client';
+import type { JMAPSession } from '../types';
+import { setKnownAccounts } from '../../lib/account-utils';
+
+// Start-up used to wait for the server's session document before the
+// account could show. The client now keeps the last one per account and
+// starts from it (loadAccountFromCache), then fetches a fresh one.
+
+const ACCOUNT = 'user@mail.example.com';
+const CREDS = { serverUrl: 'https://mail.example.com', username: 'user', password: 'pass' };
+
+const SESSION: JMAPSession = {
+  apiUrl: 'https://mail.example.com/jmap/',
+  downloadUrl: 'https://mail.example.com/download/{accountId}/{blobId}/{name}?type={type}',
+  uploadUrl: 'https://mail.example.com/upload/{accountId}/',
+  eventSourceUrl: 'https://mail.example.com/eventsource/',
+  primaryAccounts: { 'urn:ietf:params:jmap:mail': 'acc-1', 'urn:ietf:params:jmap:core': 'acc-1' },
+  accounts: { 'acc-1': { name: 'user@example.com', isPersonal: true, isReadOnly: false } },
+  capabilities: { 'urn:ietf:params:jmap:core': {}, 'urn:ietf:params:jmap:mail': {} },
+  state: 'state-1',
+};
+
+function mockFetch(responses: Array<{ status: number; json?: unknown }>) {
+  let i = 0;
+  const fn = vi.fn(async (url: string) => {
+    const r = responses[i++] ?? responses[responses.length - 1];
+    return {
+      ok: r.status >= 200 && r.status < 300,
+      status: r.status,
+      statusText: r.status === 200 ? 'OK' : 'Error',
+      url,
+      redirected: false,
+      headers: { get: () => null },
+      json: async () => r.json,
+      text: async () => (r.json === undefined ? '' : JSON.stringify(r.json)),
+    };
+  });
+  vi.stubGlobal('fetch', fn);
+  return fn;
+}
+
+async function storeCredentials() {
+  const SecureStore = await import('expo-secure-store');
+  await SecureStore.setItemAsync(`jmap_credentials__${ACCOUNT.replace(/[^a-zA-Z0-9._-]/g, '_')}`, JSON.stringify(CREDS));
+}
+
+beforeEach(async () => {
+  secure.clear();
+  await AsyncStorage.clear();
+});
+
+afterEach(() => {
+  vi.unstubAllGlobals();
+  vi.restoreAllMocks();
+  setKnownAccounts([]);
+});
+
+describe('saved session', () => {
+  it('starts from the session of the last connect, without a request', async () => {
+    await storeCredentials();
+    mockFetch([{ status: 200, json: SESSION }]);
+    expect(await new JMAPClient().loadAccount(ACCOUNT)).toBe(true);
+    await vi.waitFor(async () => expect(await AsyncStorage.getAllKeys()).toHaveLength(1));
+
+    const fetch = mockFetch([{ status: 500 }]);
+    const client = new JMAPClient();
+    expect(await client.loadAccountFromCache(ACCOUNT)).toBe(true);
+    expect(fetch).not.toHaveBeenCalled();
+    expect(client.accountId).toBe('acc-1');
+    expect(client.currentSession?.apiUrl).toBe(SESSION.apiUrl);
+  });
+
+  it('has nothing to start from before the first connect', async () => {
+    await storeCredentials();
+    expect(await new JMAPClient().loadAccountFromCache(ACCOUNT)).toBe(false);
+  });
+
+  it('ignores a session saved for another server', async () => {
+    await storeCredentials();
+    await AsyncStorage.setItem(
+      `jmap_session_cache__${ACCOUNT}`,
+      JSON.stringify({ serverUrl: 'https://old.example.com', session: SESSION }),
+    );
+    expect(await new JMAPClient().loadAccountFromCache(ACCOUNT)).toBe(false);
+  });
+
+  it('is dropped with the credentials', async () => {
+    await storeCredentials();
+    await AsyncStorage.setItem(
+      `jmap_session_cache__${ACCOUNT}`,
+      JSON.stringify({ serverUrl: CREDS.serverUrl, session: SESSION }),
+    );
+    await new JMAPClient().clearAccountCredentials(ACCOUNT);
+    expect(await AsyncStorage.getItem(`jmap_session_cache__${ACCOUNT}`)).toBeNull();
+  });
+
+  it('revalidates against the server and reports refused credentials', async () => {
+    await storeCredentials();
+    await AsyncStorage.setItem(
+      `jmap_session_cache__${ACCOUNT}`,
+      JSON.stringify({ serverUrl: CREDS.serverUrl, session: SESSION }),
+    );
+    const client = new JMAPClient();
+    await client.loadAccountFromCache(ACCOUNT);
+    mockFetch([{ status: 401 }]);
+    await expect(client.revalidateSession()).rejects.toBeInstanceOf(AuthenticationError);
+  });
+
+  it('drops a revalidation that finishes after a switch to another account', async () => {
+    await storeCredentials();
+    await AsyncStorage.setItem(
+      `jmap_session_cache__${ACCOUNT}`,
+      JSON.stringify({ serverUrl: CREDS.serverUrl, session: SESSION }),
+    );
+    const client = new JMAPClient();
+    await client.loadAccountFromCache(ACCOUNT);
+    mockFetch([{ status: 200, json: { ...SESSION, apiUrl: 'https://mail.example.com/jmap2/' } }]);
+    const pending = client.revalidateSession();
+    client.reset();
+    expect(await pending).toBeNull();
+    expect(client.currentSession).toBeNull();
+  });
+});
+
+// Account changes overlap (a switch while the start is still reading the
+// saved session, or while it checks it with the server). The client's
+// session epoch decides which one owns the client; the saved-session start
+// takes part in it like any load.
+describe('saved session and overlapping account changes', () => {
+  const OTHER = 'other@mail.example.com';
+  const OTHER_CREDS = { serverUrl: 'https://mail.example.com', username: 'other', password: 'pass2' };
+  const OTHER_SESSION: JMAPSession = {
+    ...SESSION,
+    primaryAccounts: { 'urn:ietf:params:jmap:mail': 'acc-2', 'urn:ietf:params:jmap:core': 'acc-2' },
+    accounts: { 'acc-2': { name: 'other@example.com', isPersonal: true, isReadOnly: false } },
+  };
+
+  async function saveSession() {
+    await storeCredentials();
+    await AsyncStorage.setItem(
+      `jmap_session_cache__${ACCOUNT}`,
+      JSON.stringify({ serverUrl: CREDS.serverUrl, session: SESSION }),
+    );
+  }
+
+  it('does not let a saved session read before a switch land after it', async () => {
+    await saveSession();
+    const SecureStore = await import('expo-secure-store');
+    await SecureStore.setItemAsync(`jmap_credentials__${OTHER.replace(/[^a-zA-Z0-9._-]/g, '_')}`, JSON.stringify(OTHER_CREDS));
+
+    // The saved session comes off storage slowly.
+    let release!: () => void;
+    const gate = new Promise<void>((r) => { release = r; });
+    const realGetItem = AsyncStorage.getItem.bind(AsyncStorage);
+    vi.spyOn(AsyncStorage, 'getItem').mockImplementationOnce(async (key: string) => {
+      await gate;
+      return realGetItem(key);
+    });
+
+    const client = new JMAPClient();
+    const cachedStart = client.loadAccountFromCache(ACCOUNT);
+    mockFetch([{ status: 200, json: OTHER_SESSION }]);
+    expect(await client.loadAccount(OTHER)).toBe(true);
+    release();
+
+    await expect(cachedStart).rejects.toBeInstanceOf(SessionSupersededError);
+    expect(client.accountId).toBe('acc-2');
+    expect(client.username).toBe('other');
+  });
+
+  it('drops a check of the saved session when a snapshot is put back meanwhile', async () => {
+    await saveSession();
+    const client = new JMAPClient();
+    await client.loadAccountFromCache(ACCOUNT);
+    const left = client.snapshot();
+    mockFetch([{ status: 200, json: { ...SESSION, apiUrl: 'https://mail.example.com/jmap2/' } }]);
+
+    const pending = client.revalidateSession();
+    // A switch that failed puts the account back: same credentials, but a
+    // newer account change than the check.
+    client.restoreSnapshot(left);
+
+    expect(await pending).toBeNull();
+    expect(client.currentSession?.apiUrl).toBe(SESSION.apiUrl);
+  });
+
+  it('keeps a check of the saved session across a credential update of the same account', async () => {
+    await saveSession();
+    const client = new JMAPClient();
+    await client.loadAccountFromCache(ACCOUNT);
+    mockFetch([{ status: 200, json: { ...SESSION, apiUrl: 'https://mail.example.com/jmap2/' } }]);
+
+    const pending = client.revalidateSession();
+    // A password change replaces the credentials object; the account and
+    // the account change are the same.
+    await client.updatePassword('new-pass');
+
+    expect((await pending)?.apiUrl).toBe('https://mail.example.com/jmap2/');
+    expect(client.currentSession?.apiUrl).toBe('https://mail.example.com/jmap2/');
+  });
+
+  it('serves nothing on credentials the server refused', async () => {
+    await saveSession();
+    const client = new JMAPClient();
+    await client.loadAccountFromCache(ACCOUNT);
+    mockFetch([{ status: 401 }]);
+
+    await expect(client.revalidateSession()).rejects.toBeInstanceOf(AuthenticationError);
+    expect(client.currentSession).toBeNull();
+    expect(client.isConnected).toBe(false);
+  });
+});
+
+// Accounts signed in before ports were part of ids keep username@host
+// (generateAccountId with the registry). The saved session is keyed by the
+// same id, so a host-only account and the account of another server on the
+// same host never read each other's.
+describe('saved session keys', () => {
+  const HOST_ONLY = 'usera@10.10.10.62';
+  const PORT = 'usera@10.10.10.62:8016';
+  const LEGACY_CREDS = { serverUrl: 'http://10.10.10.62:8120', username: 'usera', password: 'a' };
+  const PORT_CREDS = { serverUrl: 'http://10.10.10.62:8016', username: 'usera', password: 'b' };
+  const sessionAt = (base: string, jmapAccount: string): JMAPSession => ({
+    ...SESSION,
+    apiUrl: `${base}/jmap/`,
+    downloadUrl: `${base}/download/{accountId}/{blobId}/{name}?type={type}`,
+    uploadUrl: `${base}/upload/{accountId}/`,
+    eventSourceUrl: `${base}/eventsource/`,
+    primaryAccounts: { 'urn:ietf:params:jmap:mail': jmapAccount, 'urn:ietf:params:jmap:core': jmapAccount },
+    accounts: { [jmapAccount]: { name: 'usera', isPersonal: true, isReadOnly: false } },
+  });
+
+  async function storeBoth() {
+    const SecureStore = await import('expo-secure-store');
+    const key = (id: string) => `jmap_credentials__${id.replace(/[^a-zA-Z0-9._-]/g, '_')}`;
+    await SecureStore.setItemAsync(key(HOST_ONLY), JSON.stringify(LEGACY_CREDS));
+    await SecureStore.setItemAsync(key(PORT), JSON.stringify(PORT_CREDS));
+    setKnownAccounts([
+      { id: HOST_ONLY, username: 'usera', serverUrl: LEGACY_CREDS.serverUrl },
+      { id: PORT, username: 'usera', serverUrl: PORT_CREDS.serverUrl },
+    ]);
+  }
+
+  it('keeps the host-only account and the port account apart', async () => {
+    await storeBoth();
+    mockFetch([{ status: 200, json: sessionAt('http://10.10.10.62:8120', 'a') }]);
+    await new JMAPClient().loadAccount(HOST_ONLY);
+    mockFetch([{ status: 200, json: sessionAt('http://10.10.10.62:8016', 'b') }]);
+    await new JMAPClient().loadAccount(PORT);
+    await vi.waitFor(async () => expect(await AsyncStorage.getAllKeys()).toHaveLength(2));
+
+    expect([...(await AsyncStorage.getAllKeys())].sort()).toEqual([
+      `jmap_session_cache__${HOST_ONLY}`,
+      `jmap_session_cache__${PORT}`,
+    ]);
+    mockFetch([{ status: 500 }]);
+    const legacy = new JMAPClient();
+    expect(await legacy.loadAccountFromCache(HOST_ONLY)).toBe(true);
+    expect(legacy.accountId).toBe('a');
+    const port = new JMAPClient();
+    expect(await port.loadAccountFromCache(PORT)).toBe(true);
+    expect(port.accountId).toBe('b');
+  });
+
+  it('saves a re-read session under the id the account was loaded with', async () => {
+    await storeBoth();
+    mockFetch([{ status: 200, json: sessionAt('http://10.10.10.62:8120', 'a') }]);
+    const client = new JMAPClient();
+    await client.loadAccount(HOST_ONLY);
+    await vi.waitFor(async () => expect(await AsyncStorage.getAllKeys()).toHaveLength(1));
+
+    // The registry is read again (the headless task fills it from storage,
+    // an account entry follows its stored server): the session stays with
+    // the account it was loaded for, not with username@host:port.
+    setKnownAccounts([]);
+    mockFetch([{ status: 200, json: { ...sessionAt('http://10.10.10.62:8120', 'a'), state: 'state-2' } }]);
+    await client.refreshSession();
+    await vi.waitFor(async () => {
+      const saved = JSON.parse((await AsyncStorage.getItem(`jmap_session_cache__${HOST_ONLY}`))!);
+      expect(saved.session.state).toBe('state-2');
+    });
+    expect(await AsyncStorage.getItem('jmap_session_cache__usera@10.10.10.62:8120')).toBeNull();
+  });
+});

src/api/jmap-client.ts

@@ -1,4 +1,5 @@
 import * as SecureStore from 'expo-secure-store';
+import AsyncStorage from '@react-native-async-storage/async-storage';
 import type {
   JMAPSession,
   JMAPMethodCall,
@@ -46,6 +47,20 @@ export function credentialsKey(accountId: string): string {
   return CREDENTIALS_PREFIX + accountId.replace(/[^a-zA-Z0-9._-]/g, '_');
 }
 
+// The session document from the account's last connect (URLs, account ids,
+// capabilities; no secrets). Start-up uses it to show the account without
+// waiting for the network, then fetches a fresh one (revalidateSession).
+const SESSION_CACHE_PREFIX = 'jmap_session_cache__';
+
+function sessionCacheKey(accountId: string): string {
+  return SESSION_CACHE_PREFIX + accountId;
+}
+
+interface CachedSession {
+  serverUrl: string;
+  session: JMAPSession;
+}
+
 export interface StoredCredentials {
   serverUrl: string;
   username: string;
@@ -155,6 +170,12 @@ export class JMAPClient {
    * install it (see SessionSupersededError).
    */
   private sessionEpoch = 0;
+  /**
+   * The local account id the session was loaded or signed in for, which
+   * keys its saved session document (rememberSession). Null while no
+   * session is up.
+   */
+  private sessionCacheId: string | null = null;
   private firstTouchGate = new FirstTouchGate();
   private rateLimitedUntil = 0;
   private authFailureListeners = new Set<(err: AuthenticationError) => void>();
@@ -301,6 +322,7 @@ export class JMAPClient {
     this.firstTouchGate.reset();
 
     const accountId = generateAccountId(username, baseUrl);
+    this.sessionCacheId = accountId;
     await writeSharedSecret(credentialsKey(accountId), JSON.stringify(credentials));
 
     return session;
@@ -380,6 +402,7 @@ export class JMAPClient {
     this.credentials = credentials;
 
     const accountId = generateAccountId(username, baseUrl);
+    this.sessionCacheId = accountId;
     await writeSharedSecret(credentialsKey(accountId), JSON.stringify(credentials));
 
     return { session, username, accountId };
@@ -427,6 +450,7 @@ export class JMAPClient {
     this.credentials = credentials;
 
     const accountId = generateAccountId(username, baseUrl);
+    this.sessionCacheId = accountId;
     await writeSharedSecret(credentialsKey(accountId), JSON.stringify(credentials));
 
     return { session, username, accountId };
@@ -671,6 +695,8 @@ export class JMAPClient {
     const session = this.rewriteSessionUrls(fetched, creds.serverUrl);
     this.session = session;
     this._accountId = this.resolveAccountId(session);
+    this.sessionCacheId = accountId;
+    this.rememberSession();
     return true;
   }
 
@@ -685,6 +711,7 @@ export class JMAPClient {
   private detachSession(): number {
     this.session = null;
     this._accountId = null;
+    this.sessionCacheId = null;
     this.sessionEpoch += 1;
     return this.sessionEpoch;
   }
@@ -699,6 +726,94 @@ export class JMAPClient {
     if (epoch !== this.sessionEpoch) throw new SessionSupersededError();
   }
 
+  /**
+   * Start-up without a network round trip: the account's credentials and the
+   * session document saved at its last connect. Returns false when either is
+   * missing (or the saved one is for another server); the caller then uses
+   * loadAccount. A wrong password or revoked token surfaces on the first
+   * request (401, onAuthFailure) or in revalidateSession. Like loadAccount it
+   * hands the client to the account at once, and throws
+   * SessionSupersededError when another account change began while the saved
+   * session was read: that one owns the client.
+   */
+  async loadAccountFromCache(accountId: string): Promise<boolean> {
+    const epoch = this.detachSession();
+    const [stored, cachedRaw] = await Promise.all([
+      SecureStore.getItemAsync(credentialsKey(accountId)),
+      AsyncStorage.getItem(sessionCacheKey(accountId)).catch(() => null),
+    ]);
+    this.assertCurrentSession(epoch);
+    if (!stored || !cachedRaw) return false;
+    let creds: StoredCredentials;
+    let cached: CachedSession;
+    try {
+      creds = JSON.parse(stored);
+      cached = JSON.parse(cachedRaw);
+    } catch {
+      return false;
+    }
+    if (!cached?.session?.apiUrl || cached.serverUrl !== creds.serverUrl) return false;
+    let accountIdInSession: string;
+    try {
+      accountIdInSession = this.resolveAccountId(cached.session);
+    } catch {
+      return false;
+    }
+    // As in loadAccount: iOS credentials saved before the notification
+    // extension existed move to the keychain group it can read.
+    void moveToSharedGroup(credentialsKey(accountId)).catch(() => undefined);
+    this.credentials = creds;
+    this.firstTouchGate.reset();
+    this.session = cached.session;
+    this._accountId = accountIdInSession;
+    this.sessionCacheId = accountId;
+    return true;
+  }
+
+  /**
+   * Fetch a fresh session document for the account the client holds now,
+   * after a start from the saved one. Resolves null when the client was
+   * handed to another account meanwhile (a switch, sign-in, sign-out or a
+   * snapshot put back: the session epoch moved), and the result is dropped.
+   * On a failure the saved session goes, as loadAccount leaves none behind,
+   * and the error is thrown: AuthenticationError for refused credentials,
+   * anything else for a server that could not be reached.
+   */
+  async revalidateSession(): Promise<JMAPSession | null> {
+    const creds = this.credentials;
+    if (!creds || !this.session) return null;
+    const epoch = this.sessionEpoch;
+    let fresh: JMAPSession;
+    let accountIdInSession: string;
+    try {
+      fresh = this.rewriteSessionUrls(await this.fetchSession(creds.serverUrl), creds.serverUrl);
+      if (epoch !== this.sessionEpoch) return null;
+      accountIdInSession = this.resolveAccountId(fresh);
+    } catch (err) {
+      if (epoch !== this.sessionEpoch) return null;
+      this.session = null;
+      this._accountId = null;
+      throw err;
+    }
+    this.session = fresh;
+    this._accountId = accountIdInSession;
+    this.rememberSession();
+    return fresh;
+  }
+
+  /**
+   * Save the live session document for the next start, under the local
+   * account id the session was loaded for (the registry's, which for an
+   * account signed in before ports were part of ids is username@host).
+   */
+  private rememberSession(): void {
+    if (!this.session || !this.credentials) return;
+    const accountId = this.sessionCacheId
+      ?? generateAccountId(this.credentials.username, this.credentials.serverUrl);
+    const entry: CachedSession = { serverUrl: this.credentials.serverUrl, session: this.session };
+    void AsyncStorage.setItem(sessionCacheKey(accountId), JSON.stringify(entry)).catch(() => undefined);
+  }
+
   /**
    * Snapshot of the live connection so a failed "add account" / switch can put
    * the previous account back without a network round-trip.
@@ -708,6 +823,7 @@ export class JMAPClient {
       session: this.session,
       credentials: this.credentials,
       accountId: this._accountId,
+      sessionCacheId: this.sessionCacheId,
     };
   }
 
@@ -716,17 +832,20 @@ export class JMAPClient {
     this.session = snap.session;
     this.credentials = snap.credentials;
     this._accountId = snap.accountId;
+    this.sessionCacheId = snap.sessionCacheId ?? null;
     this.firstTouchGate.reset();
   }
 
   async clearAccountCredentials(accountId: string): Promise<void> {
     await SecureStore.deleteItemAsync(credentialsKey(accountId));
+    await AsyncStorage.removeItem(sessionCacheKey(accountId)).catch(() => undefined);
   }
 
   async clearAllCredentials(accountIds: string[]): Promise<void> {
     await Promise.all([
       SecureStore.deleteItemAsync(LEGACY_CREDENTIALS_KEY),
       ...accountIds.map((id) => SecureStore.deleteItemAsync(credentialsKey(id))),
+      ...accountIds.map((id) => AsyncStorage.removeItem(sessionCacheKey(id)).catch(() => undefined)),
     ]);
   }
 
@@ -788,6 +907,7 @@ export class JMAPClient {
     this.session = null;
     this.credentials = null;
     this._accountId = null;
+    this.sessionCacheId = null;
     this.firstTouchGate.reset();
     this.rateLimitedUntil = 0;
   }
@@ -800,6 +920,7 @@ export class JMAPClient {
     await SecureStore.deleteItemAsync(LEGACY_CREDENTIALS_KEY);
     if (currentAccountId) {
       await SecureStore.deleteItemAsync(credentialsKey(currentAccountId));
+      await AsyncStorage.removeItem(sessionCacheKey(currentAccountId)).catch(() => undefined);
     }
   }
 
@@ -1023,6 +1144,7 @@ export class JMAPClient {
     const session = this.rewriteSessionUrls(fetched, baseUrl);
     this.session = session;
     this._accountId = this.resolveAccountId(session);
+    this.rememberSession();
     return session;
   }
 
@@ -1390,6 +1512,8 @@ export interface ClientSnapshot {
   session: JMAPSession | null;
   credentials: StoredCredentials | null;
   accountId: string | null;
+  /** The local account id the session's saved document is kept under. */
+  sessionCacheId?: string | null;
 }
 
 // ── URL helpers ──────────────────────────────────────────

src/stores/__tests__/auth-store-server-change.test.ts

@@ -28,6 +28,12 @@ const { client } = vi.hoisted(() => {
     client: {
       session,
       requests: [] as Array<Array<[string, Record<string, unknown>, string]>>,
+      // Milliseconds each request takes (0: answered on the next tick).
+      latency: 0,
+      // The new server takes the old states, and skips the changes since.
+      acceptsOldStates: false,
+      // What the new server's Mailbox/get lists.
+      mailboxes: [] as unknown[],
     },
   };
 });
@@ -35,6 +41,9 @@ const { client } = vi.hoisted(() => {
 vi.mock('../../api/jmap-client', () => ({
   jmapClient: {
     loadAccount: vi.fn(async () => true),
+    loadAccountFromCache: vi.fn(async () => false),
+    revalidateSession: vi.fn(async () => null),
+    getStoredCredentials: vi.fn(async () => null),
     consumeLegacyCredentials: vi.fn(async () => null),
     clearAccountCredentials: vi.fn(async () => undefined),
     reset: vi.fn(),
@@ -51,12 +60,18 @@ vi.mock('../../api/jmap-client', () => ({
     getAccountName: () => 'user',
     request: vi.fn(async (calls: Array<[string, Record<string, unknown>, string]>) => {
       client.requests.push(calls);
+      if (client.latency) await new Promise((r) => setTimeout(r, client.latency));
       // The 1.0 server knows nothing of the 0.16.23 states.
       return {
         methodResponses: calls.map(([name, args, id]) => (name.endsWith('/changes')
-          ? ['error', { type: 'cannotCalculateChanges' }, id]
+          ? (client.acceptsOldStates
+            ? [name, {
+              accountId: args.accountId, oldState: args.sinceState, newState: 'sfy',
+              created: [], updated: [], destroyed: [], hasMoreChanges: false,
+            }, id]
+            : ['error', { type: 'cannotCalculateChanges' }, id])
           : [name, {
-            accountId: args.accountId, state: 'sfy', list: [], notFound: [],
+            accountId: args.accountId, state: 'sfy', list: name === 'Mailbox/get' ? client.mailboxes : [], notFound: [],
             ...(name === 'Email/set'
               ? { updated: Object.fromEntries(Object.keys((args.update ?? {}) as object).map((k) => [k, null])) }
               : {}),
@@ -65,6 +80,7 @@ vi.mock('../../api/jmap-client', () => ({
     }),
     getStoredOAuthTokens: vi.fn(async () => null),
     accountId: 'f',
+    connectedAccountId: 'f',
     isConnected: true,
     currentSession: client.session('1.0'),
     username: 'user',
@@ -72,6 +88,7 @@ vi.mock('../../api/jmap-client', () => ({
   },
   AuthenticationError: class AuthenticationError extends Error {},
   NetworkError: class NetworkError extends Error {},
+  SessionSupersededError: class SessionSupersededError extends Error {},
 }));
 
 vi.mock('../../lib/push-notifications', () => ({
@@ -103,6 +120,9 @@ beforeEach(async () => {
   vi.spyOn(console, 'warn').mockImplementation(() => undefined);
   await AsyncStorage.clear();
   client.requests.length = 0;
+  client.latency = 0;
+  client.acceptsOldStates = false;
+  client.mailboxes = [];
   // A cold start: nothing is attached yet.
   await useOutboxStore.getState().setAccount(null);
   await useOfflineCacheStore.getState().setAccount(null);
@@ -208,3 +228,61 @@ describe('restoring the session on a replaced server', () => {
     expect(await readServerFingerprint(ACCOUNT)).toBe(sessionFingerprint(session('1.0')));
   });
 });
+
+// A start from the session saved at the last connect sends its reads with
+// that session, before the server answered. Until the server confirmed the
+// session and its check ran, the queue waits; on a replaced server what the
+// early reads bring back is dropped with the rest, never kept.
+describe('starting from the saved session', () => {
+  async function startFromSavedSession(server: string) {
+    const { jmapClient } = await import('../../api/jmap-client');
+    vi.mocked(jmapClient.loadAccountFromCache).mockResolvedValueOnce(true);
+    let confirm!: () => void;
+    vi.mocked(jmapClient.revalidateSession).mockReturnValueOnce(
+      new Promise((resolve) => { confirm = () => resolve(session(server)); }),
+    );
+    expect(await useAuthStore.getState().restoreSession()).toBe(true);
+    return confirm;
+  }
+
+  it('sends the queue only once the server confirmed the saved session (Stalwart 1.0)', async () => {
+    await writeServerFingerprint(ACCOUNT, sessionFingerprint(session('1.0')));
+    await AsyncStorage.setItem(OUTBOX_KEY, JSON.stringify(QUEUED));
+
+    const confirm = await startFromSavedSession('1.0');
+    await new Promise((r) => setTimeout(r, 20));
+    // The reads went out without waiting; the queue did not.
+    expect(client.requests.flat().some(([name]) => name === 'Mailbox/changes')).toBe(true);
+    expect(emailSets()).toEqual([]);
+
+    confirm();
+    await vi.waitFor(() => expect(emailSets()).toHaveLength(1));
+    expect(emailSets()[0][1]).toEqual({ accountId: 'f', update: { b: { 'keywords/$seen': true } } });
+  });
+
+  it('keeps nothing the early reads brought back from a replaced server (Stalwart 0.16.23 to 1.0)', async () => {
+    await writeServerFingerprint(ACCOUNT, sessionFingerprint(session('0.16.23')));
+    await AsyncStorage.setItem(OUTBOX_KEY, JSON.stringify(QUEUED));
+    // The early reads are still on their way when the session arrives, and
+    // the new server answers the old folder state with "no changes".
+    client.latency = 40;
+    client.acceptsOldStates = true;
+    client.mailboxes = [{
+      id: 'm1', name: 'Inbox', role: 'inbox', parentId: null, sortOrder: 0,
+      totalEmails: 0, unreadEmails: 0, totalThreads: 0, unreadThreads: 0, myRights: {}, isSubscribed: true,
+    }];
+
+    const confirm = await startFromSavedSession('1.0');
+    confirm();
+    await vi.waitFor(async () => expect(await readServerFingerprint(ACCOUNT)).toBe(sessionFingerprint(session('1.0'))));
+    await new Promise((r) => setTimeout(r, 150));
+
+    const email = useEmailStore.getState();
+    expect(JSON.stringify([email.mailboxState, email.emailStates, email.queryState, email.mailboxSnapshots])).not.toContain('s1iaq');
+    // The folder list was read again after the drop, from the new server.
+    expect(email.mailboxes.map((m) => m.id)).toEqual(['m1']);
+    expect(emailSets()).toEqual([]);
+    expect(useOutboxStore.getState().entries).toEqual([]);
+    expect(await AsyncStorage.getItem(OUTBOX_KEY)).toBeNull();
+  });
+});

src/stores/__tests__/auth-store.test.ts

@@ -6,6 +6,8 @@ vi.mock('../../api/jmap-client', () => ({
     logout: vi.fn(),
     restoreSession: vi.fn(),
     loadAccount: vi.fn(),
+    loadAccountFromCache: vi.fn(async () => false),
+    revalidateSession: vi.fn(async () => null),
     consumeLegacyCredentials: vi.fn(async () => null),
     clearAccountCredentials: vi.fn(async () => undefined),
     clearAllCredentials: vi.fn(async () => undefined),
@@ -17,7 +19,9 @@ vi.mock('../../api/jmap-client', () => ({
     hasAccountCapability: vi.fn(() => false),
     request: vi.fn(async () => { throw new Error('not mocked'); }),
     getStoredOAuthTokens: vi.fn(async () => null),
+    getStoredCredentials: vi.fn(async () => null),
     accountId: 'acc-1',
+    connectedAccountId: 'acc-1',
     currentSession: { apiUrl: 'https://mail.example.com/jmap/' },
     username: 'user',
     serverUrl: 'https://mail.example.com',
@@ -28,6 +32,7 @@ vi.mock('../../api/jmap-client', () => ({
   NetworkError: class NetworkError extends Error {
     constructor(msg: string) { super(msg); this.name = 'NetworkError'; }
   },
+  SessionSupersededError: class SessionSupersededError extends Error {},
 }));
 
 vi.mock('../../lib/push-notifications', () => ({
@@ -35,12 +40,13 @@ vi.mock('../../lib/push-notifications', () => ({
   teardownPushNotificationsForAccount: vi.fn(async () => undefined),
 }));
 
-import { jmapClient } from '../../api/jmap-client';
+import { jmapClient, AuthenticationError, NetworkError } from '../../api/jmap-client';
 import { useAuthStore, HYDRATION_TIMEOUT_MS } from '../auth-store';
 import { useAccountStore } from '../account-store';
 import { useCalendarStore } from '../calendar-store';
 import { useContactsStore } from '../contacts-store';
 import { useEmailStore } from '../email-store';
+import { useOutboxStore } from '../outbox-store';
 import type { Email } from '../../api/types';
 import { peekRow, rememberRows } from '../../lib/email-detail-cache';
 import { bodyDocument } from '../../lib/email-body-document';
@@ -49,6 +55,8 @@ import { lastBodyHeight, rememberBodyHeight } from '../../lib/body-heights';
 const mockConnect = jmapClient.connect as ReturnType<typeof vi.fn>;
 const mockLogout = jmapClient.logout as ReturnType<typeof vi.fn>;
 const mockLoadAccount = jmapClient.loadAccount as ReturnType<typeof vi.fn>;
+const mockLoadFromCache = jmapClient.loadAccountFromCache as ReturnType<typeof vi.fn>;
+const mockRevalidate = jmapClient.revalidateSession as ReturnType<typeof vi.fn>;
 
 function resetAccountStore(): void {
   useAccountStore.setState({
@@ -236,6 +244,173 @@ describe('auth-store', () => {
       expect(useAuthStore.getState().isAuthenticated).toBe(true);
     });
 
+    describe('from the session saved at the last connect', () => {
+      const account = (id: string, isDefault: boolean) => ({
+        id, serverUrl: 'https://mail.example.com', username: id,
+        displayName: id, email: id, avatarColor: '#000', lastLoginAt: 0,
+        isConnected: true, hasError: false, isDefault,
+      });
+
+      function registerAccount() {
+        useAccountStore.setState({
+          accounts: [account('acc-1', true)],
+          activeAccountId: 'acc-1',
+          defaultAccountId: 'acc-1',
+        });
+      }
+
+      function registerTwoAccounts() {
+        useAccountStore.setState({
+          accounts: [account('acc-1', true), account('acc-2', false)],
+          activeAccountId: 'acc-1',
+          defaultAccountId: 'acc-1',
+        });
+      }
+
+      function deferred<T>() {
+        let resolve!: (value: T) => void;
+        let reject!: (err: unknown) => void;
+        const promise = new Promise<T>((res, rej) => { resolve = res; reject = rej; });
+        return { promise, resolve, reject };
+      }
+
+      const resume = vi.fn(async () => undefined);
+      const realResume = useOutboxStore.getState().resume;
+      beforeEach(() => {
+        // clearAllMocks keeps queued once-values; a test that fails early
+        // must not hand its leftovers to the next one.
+        mockLoadAccount.mockReset();
+        mockLoadFromCache.mockReset().mockResolvedValue(false);
+        mockRevalidate.mockReset().mockResolvedValue(null);
+        resume.mockClear();
+        useOutboxStore.setState({ resume });
+        return () => useOutboxStore.setState({ resume: realResume });
+      });
+
+      // Start-up used to wait for the server's session document before the
+      // cached inbox could show.
+      it('shows the account without waiting for the server', async () => {
+        registerAccount();
+        mockLoadFromCache.mockResolvedValueOnce(true);
+        mockRevalidate.mockReturnValueOnce(new Promise(() => undefined));
+
+        const restored = await useAuthStore.getState().restoreSession();
+
+        expect(restored).toBe(true);
+        expect(useAuthStore.getState().isAuthenticated).toBe(true);
+        expect(useAuthStore.getState().activeAccountId).toBe('acc-1');
+        expect(mockLoadAccount).not.toHaveBeenCalled();
+        expect(mockRevalidate).toHaveBeenCalledTimes(1);
+      });
+
+      // What waits for a live session (push setup, the offline sync, the
+      // outbox) must not run on the saved one before the server confirmed it
+      // and its server check ran.
+      it('counts the session as live, and resumes the outbox, only once the server confirmed it', async () => {
+        registerAccount();
+        mockLoadFromCache.mockResolvedValueOnce(true);
+        const check = deferred<unknown>();
+        mockRevalidate.mockReturnValueOnce(check.promise);
+
+        await useAuthStore.getState().restoreSession();
+        await new Promise((r) => setTimeout(r, 10));
+
+        expect(useAuthStore.getState().session).toBeNull();
+        expect(resume).not.toHaveBeenCalledWith('acc-1');
+
+        check.resolve({ apiUrl: 'https://mail.example.com/jmap/' });
+        await vi.waitFor(() => expect(useAuthStore.getState().session).not.toBeNull());
+        expect(resume).toHaveBeenCalledWith('acc-1');
+        expect(useAccountStore.getState().accounts[0]).toMatchObject({ isConnected: true, hasError: false });
+      });
+
+      // A 401 used to evict the account (and everything kept for it) with
+      // "Session expired".
+      it('keeps the account for a new sign-in when the server refuses the stored credentials', async () => {
+        registerAccount();
+        mockLoadFromCache.mockResolvedValueOnce(true);
+        mockRevalidate.mockRejectedValueOnce(new AuthenticationError('Invalid credentials'));
+
+        await useAuthStore.getState().restoreSession();
+        await vi.waitFor(() => expect(useAuthStore.getState().reauth).not.toBeNull());
+
+        expect(useAuthStore.getState().reauth).toMatchObject({ accountId: 'acc-1' });
+        expect(useAuthStore.getState().isAuthenticated).toBe(true);
+        expect(useAuthStore.getState().session).toBeNull();
+        expect(useAccountStore.getState().accounts).toHaveLength(1);
+        expect(useAccountStore.getState().accounts[0]).toMatchObject({ needsSignIn: true, isConnected: false });
+        // The refusal is the answer: no second round trip to hear it again.
+        expect(mockLoadAccount).not.toHaveBeenCalled();
+        expect(resume).not.toHaveBeenCalledWith('acc-1');
+      });
+
+      it('stays signed in and marks the account offline without network', async () => {
+        registerAccount();
+        mockLoadFromCache.mockResolvedValueOnce(true);
+        mockRevalidate.mockRejectedValueOnce(new Error('Network request failed'));
+
+        await useAuthStore.getState().restoreSession();
+        await vi.waitFor(() => expect(useAccountStore.getState().accounts[0].hasError).toBe(true));
+
+        expect(useAuthStore.getState().isAuthenticated).toBe(true);
+        expect(useAccountStore.getState().accounts[0].isConnected).toBe(false);
+      });
+
+      it('does not start from the saved session for an account that must sign in again', async () => {
+        registerAccount();
+        useAccountStore.getState().updateAccount('acc-1', { needsSignIn: true });
+        mockLoadAccount.mockRejectedValueOnce(new AuthenticationError('Invalid credentials'));
+
+        await useAuthStore.getState().restoreSession();
+
+        expect(mockLoadFromCache).not.toHaveBeenCalled();
+        expect(useAuthStore.getState().reauth).toMatchObject({ accountId: 'acc-1' });
+      });
+
+      // The check of the saved session is the older account change once a
+      // switch began: what it learns must not land on the account in use,
+      // even when that is the same account again.
+      it('drops a refusal of the saved session that arrives after switching away and back', async () => {
+        registerTwoAccounts();
+        mockLoadFromCache.mockResolvedValueOnce(true);
+        const check = deferred<unknown>();
+        mockRevalidate.mockReturnValueOnce(check.promise);
+        await useAuthStore.getState().restoreSession();
+
+        mockLoadAccount.mockResolvedValueOnce(true).mockResolvedValueOnce(true);
+        await useAuthStore.getState().switchAccount('acc-2');
+        await useAuthStore.getState().switchAccount('acc-1');
+        expect(useAuthStore.getState().session).not.toBeNull();
+
+        check.reject(new AuthenticationError('Invalid credentials'));
+        await new Promise((r) => setTimeout(r, 10));
+
+        expect(useAuthStore.getState().activeAccountId).toBe('acc-1');
+        expect(useAuthStore.getState().session).not.toBeNull();
+        expect(useAuthStore.getState().reauth).toBeNull();
+        expect(useAccountStore.getState().getAccountById('acc-1')?.needsSignIn).toBeFalsy();
+      });
+
+      // A switch that fails puts the account back. Its saved session was
+      // never confirmed (the switch overtook the check), so the check runs
+      // again, and the outbox waits for it.
+      it('checks the saved session again when a switch that overtook the check fails', async () => {
+        registerTwoAccounts();
+        mockLoadFromCache.mockResolvedValueOnce(true);
+        mockRevalidate.mockReturnValueOnce(new Promise(() => undefined));
+        await useAuthStore.getState().restoreSession();
+
+        mockLoadAccount.mockRejectedValueOnce(new NetworkError('offline'));
+        mockRevalidate.mockResolvedValueOnce({ apiUrl: 'https://mail.example.com/jmap/' });
+        await useAuthStore.getState().switchAccount('acc-2');
+
+        expect(useAuthStore.getState().activeAccountId).toBe('acc-1');
+        expect(mockRevalidate).toHaveBeenCalledTimes(2);
+        await vi.waitFor(() => expect(useAuthStore.getState().session).not.toBeNull());
+        expect(resume).toHaveBeenCalledWith('acc-1');
+      });
+    });
+
     it('stops waiting for a persisted store that never finishes hydrating', async () => {
       vi.useFakeTimers();
       const warn = vi.spyOn(console, 'warn').mockImplementation(() => undefined);

src/stores/auth-store.ts

@@ -39,6 +39,7 @@ import {
   teardownPushNotificationsForAccount,
 } from '../lib/push-notifications';
 import { reconcileServerFingerprint } from '../lib/server-change';
+import { readServerFingerprint, sessionFingerprint } from '../lib/server-fingerprint';
 import { deviceSyncSignedIn, releaseDeviceSyncBeforeSignOut } from '../device-sync/app/lifecycle';
 import { perfMark } from '../lib/perf-marks';
 import { abortable, isSignInCancelled, throwIfCancelled } from '../lib/sign-in-abort';
@@ -213,12 +214,13 @@ function clearAccountFeatureStores(accountId: string | null): void {
 // Once a session is up and before anything reads the account's caches: when
 // the server behind it is not the one that filled them, they go (see
 // lib/server-change). A failed check never blocks signing in; it runs again
-// with the next session.
-async function checkServerChange(accountId: string, session: JMAPSession): Promise<void> {
+// with the next session. Resolves to true when the caches were dropped.
+async function checkServerChange(accountId: string, session: JMAPSession): Promise<boolean> {
   try {
-    await reconcileServerFingerprint(accountId, session);
+    return await reconcileServerFingerprint(accountId, session);
   } catch (err) {
     console.warn('[auth-store] server change check failed:', err);
+    return false;
   }
 }
 
@@ -317,6 +319,11 @@ let signInSaved: { client: ClientSnapshot; isCurrent: () => boolean } | null = n
 // the app went to the sign-in screen with every account still registered.
 let restoreUnderWay: Promise<void> | null = null;
 
+// The account a cold start brought up from the session saved at its last
+// connect, until the server confirms it (revalidateRestoredSession). Its
+// session is not live yet: its server was not checked and its outbox waits.
+let unconfirmedStart: string | null = null;
+
 async function switchesSettled(): Promise<void> {
   while (pendingSwitch) await pendingSwitch.settled;
 }
@@ -448,23 +455,31 @@ async function signIn(
 
 function refetchFeatureStores(accountId: string): void {
   resumeOutbox(accountId);
+  void reloadFeatureStores();
+}
+
+// The reads of refetchFeatureStores, without the outbox: a start from the
+// saved session runs them before the server was checked (see
+// revalidateRestoredSession). Resolves when they have all ended.
+function reloadFeatureStores(): Promise<void> {
   // Fire-and-forget: each store handles its own errors.
   const emailStore = useEmailStore.getState();
-  void emailStore.fetchMailboxes();
+  const reads: Promise<unknown>[] = [emailStore.fetchMailboxes()];
   // If a mailbox was selected before this restore (cached from last session),
   // refresh its contents so the user sees up-to-date mail without manually
   // pulling to refresh.
   if (emailStore.currentMailboxId) {
-    void emailStore.refreshEmails();
+    reads.push(emailStore.refreshEmails());
   }
-  void useContactsStore.getState().fetchContacts();
+  reads.push(useContactsStore.getState().fetchContacts());
   const calendarStore = useCalendarStore.getState();
-  void calendarStore.fetchCalendars();
+  reads.push(calendarStore.fetchCalendars());
   // Refresh the event range cached from last session (if any) so recurring
   // events reflect new invitations / cancellations without the user swiping.
   if (calendarStore.loadedRange) {
-    void calendarStore.refresh();
+    reads.push(calendarStore.refresh());
   }
+  return Promise.allSettled(reads).then(() => undefined);
 }
 
 // Pairing codes this app process has redeemed or is redeeming. Codes are
@@ -603,6 +618,9 @@ function applyConnectedState(
     client: jmapClient,
     reauth: null,
   });
+  // A session from the server, or a start from the saved one, which sets
+  // this again right after.
+  unconfirmedStart = null;
 }
 
 export const useAuthStore = create<AuthState>((set, get) => ({
@@ -990,6 +1008,8 @@ export const useAuthStore = create<AuthState>((set, get) => ({
     // leaving the previous account dead until relaunch. With switches under
     // way, that is the account the first of them left; with an add-account
     // sign-in under way, the connection it saved.
+    // (A start from the saved session is not live until the server
+    // confirmed it: its session in this store stays null till then.)
     const origin: SwitchOrigin = underWay?.origin ?? {
       accountId: get().activeAccountId,
       live: get().session !== null,
@@ -1024,6 +1044,7 @@ export const useAuthStore = create<AuthState>((set, get) => ({
         // still in the snapshot taken then, and its server was checked.
         jmapClient.restoreSnapshot(origin.client);
         if (origin.live) refetchFeatureStores(accountId);
+        else if (unconfirmedStart === accountId) void revalidateRestoredSession(accountId);
         set({ isLoading: false });
         return;
       }
@@ -1036,6 +1057,10 @@ export const useAuthStore = create<AuthState>((set, get) => ({
         // Its session and server check still hold; without one, the next
         // session resumes the outbox.
         if (origin.accountId && origin.live) resumeOutbox(origin.accountId);
+        // A start from the saved session whose check this switch overtook.
+        else if (origin.accountId && unconfirmedStart === origin.accountId) {
+          void revalidateRestoredSession(origin.accountId);
+        }
       };
       try {
         const ok = await jmapClient.loadAccount(accountId);
@@ -1170,6 +1195,48 @@ export const useAuthStore = create<AuthState>((set, get) => ({
       // data from a previous session.
       useEmailStore.getState().setActiveAccount(target.id);
 
+      // Start from the session saved at the last connect: the cached mail
+      // shows without waiting for the server, and a fresh session follows.
+      // Not for an account the server refused: only a new sign-in brings it
+      // back, and the load below asks for one.
+      let fromCache = false;
+      if (!target.needsSignIn) {
+        try {
+          fromCache = await jmapClient.loadAccountFromCache(target.id);
+        } catch (err) {
+          // A sign-in or sign-out that began meanwhile owns the client.
+          if (err instanceof SessionSupersededError) throw err;
+          fromCache = false;
+        }
+      }
+      if (fromCache) {
+        accountStore.setActiveAccount(target.id);
+        followStoredServer(target.id);
+        // The client serves the saved session, so the reads go out now. The
+        // session here stays null until the server confirmed it: what waits
+        // for a live one (push setup, the offline sync, the outbox) waits
+        // for that, as on a start without the saved session.
+        set({
+          isAuthenticated: true,
+          isLoading: false,
+          hasRestoredSession: true,
+          error: null,
+          serverUrl: target.serverUrl,
+          username: target.username,
+          session: null,
+          accountId: jmapClient.accountId,
+          activeAccountId: target.id,
+          client: jmapClient,
+          reauth: null,
+        });
+        unconfirmedStart = target.id;
+        perfMark('restore-done', { cached: true });
+        const reads = reloadFeatureStores();
+        void revalidateRestoredSession(target.id, reads);
+        void syncAccountDisplayName(target.id);
+        return true;
+      }
+
       try {
         const ok = await jmapClient.loadAccount(target.id);
         perfMark('restore-session');
@@ -1317,6 +1384,71 @@ export const useAuthStore = create<AuthState>((set, get) => ({
   clearReauth: () => set({ reauth: null }),
 }));
 
+/**
+ * After a start from the saved session: fetch a fresh one, then do what a
+ * load from the server does before the account counts as up: follow the
+ * server its credentials sign in to, check the server was not replaced, mark
+ * the account connected, put the session in this store and resume the
+ * outbox. A refused sign-in keeps the account and asks for a new one, as a
+ * load refused at start does (keepForSignIn); no network marks the account
+ * offline and drops the saved session, as a start without network does, and
+ * the session retry brings it up. A switch, sign-in or sign-out that begins
+ * meanwhile owns the client and the stores: the client drops a session that
+ * arrives after it (its epoch moved), and the stores are left alone.
+ *
+ * `reads` are the ones the start sent with the saved session. When the
+ * server may have been replaced they end before the check, so nothing they
+ * bring back lands after it dropped the caches.
+ */
+async function revalidateRestoredSession(accountId: string, reads?: Promise<void>): Promise<void> {
+  const generation = accountChange;
+  const isCurrent = () => generation === accountChange
+    && useAuthStore.getState().activeAccountId === accountId;
+  const before = jmapClient.connectedAccountId;
+  let fresh: JMAPSession | null;
+  try {
+    fresh = await jmapClient.revalidateSession();
+  } catch (err) {
+    if (!isCurrent() || err instanceof SessionSupersededError) return;
+    unconfirmedStart = null;
+    if (err instanceof AuthenticationError) {
+      const reauth = await keepForSignIn(accountId);
+      if (isCurrent()) useAuthStore.setState({ session: null, accountId: null, isLoading: false, error: null, reauth });
+      return;
+    }
+    useAccountStore.getState().updateAccount(accountId, {
+      isConnected: false,
+      hasError: true,
+      errorMessage: err instanceof Error ? err.message : String(err),
+    });
+    useAuthStore.setState({ session: null, accountId: null });
+    return;
+  }
+  if (!fresh || !isCurrent()) return;
+  followStoredServer(accountId);
+  if (reads) {
+    const recorded = await readServerFingerprint(accountId).catch(() => null);
+    if (recorded !== sessionFingerprint(fresh)) await reads;
+    if (!isCurrent()) return;
+  }
+  const dropped = await checkServerChange(accountId, fresh);
+  // A keep-alive may have read the session again meanwhile.
+  const live = jmapClient.currentSession;
+  if (!isCurrent() || !live) return;
+  unconfirmedStart = null;
+  useAccountStore.getState().updateAccount(accountId, {
+    isConnected: true,
+    hasError: false,
+    errorMessage: undefined,
+    needsSignIn: false,
+  });
+  useAuthStore.setState({ session: live, accountId: jmapClient.accountId });
+  resumeOutbox(accountId);
+  // The reads made from the saved session went to another JMAP account, or
+  // into caches the server check has just dropped.
+  if (dropped || jmapClient.connectedAccountId !== before) void reloadFeatureStores();
+}
+
 // A 401 on a live session (revoked password/token, expired refresh token)
 // used to leave the user on a dead session until relaunch: nothing outside
 // the login flow handled `AuthenticationError`, and `retrySession` bailed